Computational fluid dynamic-discrete element method coupling analysis of particle transport in branched networks

An understanding of the particle transport characteristics in a branched network helps to predict the particle distribution and prevent undesired plugging in various engineering systems.Quantitative analysis of particle flow characteristics is challenging in that experiments are expensive and particle flow is difficult to detect without disturbing the flow.To overcome this difficulty,man-made fractal tree-like branched networks were built,and a coupled computational fluid dynamic and discrete element method model was applied.A series of numerical simulations was carried out to analyze the influence of fractal structure parameters of networks on the particle flow characteristics.The joint influence of inertial,shunt capacity and superposition from upstream branches on particle flow was investigated.The injection position at the inlet determined the particle velocity and its future flow path.The particle density ratio,particle size and bifurcation angle had a greater influence on the shunting of K2 branches than that in the K1 level and N_k22/N_k21 reached a maximum at 60°.Compared with a network with an even number of branches,there was a preferential branch when the branch number was odd.The preferential branch effect or asymmetry degree of the level(K2)branches had a more significant impact on particle shunting than that from the upstream branches(K1).     

硅烷化磁铁粉固定胰蛋白酶的研究

分别以硅烷化磁铁粉、硅烷磁化脱乙酰几丁质及脱乙酰几丁质作载体,甲醛或戊二醛为交联剂,对胰蛋白酶的固定化条件及所制备的固定化酶的性质进行了研究．研究了载体种类、交联剂和ｐＨ值以及载体与酶比例等因素对胰蛋白酶固定化的影响．研究了不同载体固定胰蛋白酶的特点,证明以硅烷化试剂和甲醛作交联剂的硅烷化磁铁粉作胰蛋白酶固定化的载体具有明显优点,所制备的硅烷化磁铁粉固定化胰蛋白酶酶学性质明显优于可溶性胰蛋白酶     

几乎强幂零Γ—环所确定的根

本文讨论几乎强幂零Γ-环及其所确定的根。主要证明了:(1)Γ-环的素根类是几乎强幂零Γ-环类的最小划分;(2)由一切几乎强幂零Γ-环类所确定的下根重合于由一切无非零几乎强幂零理想的Γ-环所确定的上根。     

500—4250eV电子对CO2的散射全截面绝对测量

对中能电子与二氧化碳分子碰撞的散射全截面测量，给出５００－４２５０ｅＶ电子对ＣＯ２的绝对散射全截面。对测量结果作了曲线拟合，并与已有的实验和理论结果进行了比较     

Computational Insight into Biotransformation Profiles of Organophosphorus Flame Retardants to Their Diester Metabolites by Cytochrome P450

Biotransformation of organophosphorus flame retardants (OPFRs) mediated by cytochrome P450 enzymes (CYPs) has a potential correlation with their toxicological effects on humans. In this work, we employed five typical OPFRs including tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), tris(1-chloro-2-propyl) phosphate (TCIPP), tri(2-chloroethyl) phosphate (TCEP), triethyl phosphate (TEP), and 2-ethylhexyl diphenyl phosphate (EHDPHP), and performed density functional theory (DFT) calculations to clarify the CYP-catalyzed biotransformation of five OPFRs to their diester metabolites. The DFT results show that the reaction mechanism consists of Cα-hydroxylation and O-dealkylation steps, and the biotransformation activities of five OPFRs may follow the order of TCEP ≈ TEP ≈ EHDPHP > TCIPP > TDCIPP. We further performed molecular dynamics (MD) simulations to unravel the binding interactions of five OPFRs in the CYP3A4 isoform. Binding mode analyses demonstrate that CYP3A4-mediated metabolism of TDCIPP, TCIPP, TCEP, and TEP can produce the diester metabolites, while EHDPHP metabolism may generate para-hydroxyEHDPHP as the primary metabolite. Moreover, the EHDPHP and TDCIPP have higher binding potential to CYP3A4 than TCIPP, TCEP, and TEP. This work reports the biotransformation profiles and binding features of five OPFRs in CYP, which can provide meaningful clues for the further studies of the metabolic fates of OPFRs and toxicological effects associated with the relevant metabolites.     

High efficiency giant magnetoresistive device based on two-dimensional MXene (Mn2NO2)

Due to the unique electronic structure of half-metals, characterized by the conductivity of majority-spin and the band gap of minority-spin, these materials have emerged as suitable alternatives for the design of efficient giant magnetoresistive (GMR) devices. Based on the first-principles calculations, an excellent GMR device has been designed by using two-dimensional (2D) half-metal Mn₂NO₂. The results show that Mn₂NO₂ has sandwiched between the Au/nMn₂NO₂ (n = 1, 2, 3)/Au heterojunction and maintains its half-metallic properties. Due to the half-metallic characteristics of Mn₂NO₂, the total current of the monolayer device can reach up to 1500 nA in the ferromagnetic state. At low voltage, the maximum GMR is observed to be 1.15 × 10³¹ %. Further, by increasing the number of layers, the ultra-high GMR at low voltage is still maintained. The developed device is a spintronic device exhibiting the highest magnetoresistive ratio reported theoretically so far. Simultaneously, a significant negative differential resistance (NDR) effect is also observed in the heterojunction. Owing to its excellent half-metallic properties and 2D structure, Mn₂NO₂ is an ideal energy-saving GMR material.     

Prospective study on observations of γ-ray sources in the Galaxy using the HADAR experiment

The High Altitude Detection of Astronomical Radiation (HADAR) experiment is a refracting terrestrial telescope array based on the atmospheric Cherenkov imaging technique. It focuses the Cherenkov light emitted by extensive air showers through a large aperture water-lens system for observing very-high-energy γ-rays and cosmic rays. With the advantages of a large field-of-view (FOV) and low energy threshold, the HADAR experiment operates in a large-scale sky scanning mode to observe galactic sources. This study presents the prospects of using the HADAR experiment for the sky survey of TeV γ-ray sources from TeVCat and provids a one-year survey of statistical significance. Results from the simulation show that a total of 23 galactic point sources, including five supernova remnant sources and superbubbles, four pulsar wind nebula sources, and 14 unidentified sources, were detected in the HADAR FOV with a significance greater than 5 standard deviations (σ). The statistical significance for the Crab Nebula during one year of operation reached 346.0 σ and the one-year integral sensitivity of HADAR above 1 TeV was ~1.3%–2.4% of the flux from the Crab Nebula.     

NOVEL FORMATION AND DECAY MECHANISMS OF NANOSTRUCTURES ON THE SURFACE

For decades the research on thin-film growth has attracted considerable attention as these kinds of materials have the potential for a new generation of device application. It is known that the nuclei at the initial stage of the islands are more stable than others and certain atoms are inert while others are active. In this paper, by using kinetic Monte Carlo simulations, we will show that, when a surfactant layer is used to mediate the growth, a counter-intuitive fractal-to-compact island shape transition can be induced by increasing deposition flux or decreasing growth temperature. Specifically, we introduce a reaction-limited aggregation (RLA) theory, where the physical process controlling the island shape transition is the shielding effect of adatoms stuck to the stable islands on the incoming adatoms. Moreover, the origin of a transition from triangular to hexagonal and then to inverted triangular as well as the decay characteristics of three-dimensional islands on the surface and relations of our unique predictions with recent experiments will be discussed. Furthermore, we will present a novel idea to make use of the condensation energy of adatoms to control the island evolution along a special direction.     

咪唑类氮氧自由基的ESR波谱的酸度相关性-pH自旋探针应用研究之一

根据咪唑类氮氧自由基的结构特性合成了一系列的pH自旅探针,其ESR波谱参数均在一定范围内与介质的酸性呈明显的相关性.可望为较精确地测量化学胶束、细胞等微观体系的pH值开辟一个新的途径.本文研究了灵敏变化的pH范围与取代基的关系,得到了5种自旅探针的ESR参数-pH曲线、pKa值以及Hanmmett相关图,分析了如何通过改变取代基合成出不同pH变化范围并适用于不同生物和化学体系的pH自旅探针,最终达到付诸应用的目的.     

铜铟镓硒太阳能电池多层膜的结构分析

对于溅射后硒化和共蒸发等方法制备的铜铟镓硒（CIGS）太阳能电池薄膜,利用多种分析方法研究了CIGS多层膜的复杂结构等．研究表明：卢瑟福背散射（RBS）在分析CIGS多层膜方面具有其独特优势和可靠的结果;溅射后硒化方法制备的CIGS薄膜中,Ga和In在CIGS薄膜中呈梯度分布,这种Ga表层少而内层多的不均匀分布与Mo层没有必然关系;RBS和俄歇电子能谱分析（AES）均显示CIGS太阳能电池器件多层膜界面处存在扩散,尤其是CdS与CIGS,Mo与CIGS的界面处;X射线荧光（XRF）结果表明,电池效率最高的CIGS层中In,Ga比例为In：Ga=0．7：0.3;X射线衍射（XRD）结果显示：退火后的CIGS／Mo薄膜结晶品质得到了优化．